Immunosuppressive blood cells and methods of producing the same

ABSTRACT

The present invention refers to a method of producing immunosuppressive blood cells that can be used for the treatment of autoimmune diseases, in particular multiple sclerosis, organ graft rejection and graft-versus-host disease.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.13/001,729, filed May 25, 2011, which is the National Phase ofInternational Patent Application No. PCT/EP2009/058169, filed Jun. 30,2009, which claims priority from European Patent Application No.08011780.7, filed Jun. 30, 2008. The contents of these applications arehereby incorporated by reference in their entirety.

The present invention refers to a method of producing immunosuppressiveblood cells that can be used for the treatment of autoimmune diseases,in particular multiple sclerosis, organ graft rejection andgraft-versus-host disease.

INTRODUCTION

The role of autoantigens and autoreactive lymphocytes in the initiationand maintenance of autoimmune diseases has been controversiallydiscussed (1). Even if self-antigens were not the primordial cause ofsome autoimmune conditions, they offer a way of directing animmunosuppressive effect to the diseased organ, and therefore constitutea promising alternative to the commonly used broadly-reactiveimmunosuppressants. In a clinical trial, an immunomodulatory peptidederived from hsp60—one of the known target self antigens—was injectedinto patients with newly diagnosed type 1 diabetes. Although the studywas small, it suggested that the peptide treatment preserved endogenousinsulin production (3). Tolerance induction was also attempted by oraladministration of self-antigens. This has been tried with myelin inmultiple sclerosis (MS), collagen in RA, and insulin in type 1 diabetes.Despite success with the prevention of diseases in animal models,clinical trials attempting to treat an ongoing disease in humans havethus far been unsuccessful (4). What has been learned from animal modelsand the few clinical studies is that autoantigens must be presented in anon-immunogenic form, usually by altering their structure. A successfulexample for the latter strategy is treatment of MS patients withcopaxone—a synthetic peptide which mimics the composition of the centralnervous component, myelin basic protein (4).

Dendritic cells (DCs) are commonly thought of as strongly stimulatorycells, but DCs can also suppress the immune response (5). Evidently,evolution has developed highly efficient mechanisms for protectingtissues and organs from self-destruction, one of them being mediated byDCs (5). What nature applies for protection from self-attack might beused by man for treatment of autoimmune diseases or graft rejection.Unfortunately, natural suppressive DCs are hard to define phenotypicallyand therefore difficult to use for therapeutic applications. Forexample, it has been shown that immature DCs induce tolerance, whereasmature DCs activate immune responses (5). However, a growing body ofrecent evidence indicates that DC maturation per se is not adistinguishing feature of immunogenicity as opposed to tolerogenicity(6). It is presently believed that the development of an immunogenic ortolerogenic response depends on the net effect of antigen dose, DClineage and maturational status, DC stimulation by pathogen-derivedproducts, and the cytokine milieu (5, 6). Given the hardly predictablesuppressive function of natural DCs, a reasonable alternative fortherapeutic purposes would be the in vitro generation of inhibitory DCs.Several methods have been described for designing suppressive DCs (7). Amajor risk of deliberately generated inhibitory DCs is their potentialreversibility to a stimulatory status. Furthermore, their effectivenessmay be limited to certain species.

DETAILED DESCRIPTION

Jiga et al., (2007) Transplantation 83:347-350 describe the use ofMitomycin C for stable transformation of stimulatory into inhibitorydendritic cells. A single injection of such donor DCs into the recipientprior to heart transplantation suppressed heart allograft rejection inrats (8). However, the use of DC's bears the disadvantage that thegeneration of DC's and the maturation period may lead to variations inthe quality of the DC's, which negatively influences the reproducibilityof the approach.

Furthermore, the therapeutic use of dendritic cells is still consideredproblematic as DCs are strongly immunogenic even when converted intosuppressive cells.

Thus, the problem underlying the present invention is to provide meansfor inducing an immune tolerance without evoking the adverse effectsobserved with conventional therapies. Surprisingly, the inventors havefound out that peripheral blood mononuclear cells (PBMC's) or wholeblood treated with mitomycin C (MMC) served as powerful toleranceinducers in a rat heart transplantation model.

The strategy for controlling autoimmune reactions envisaged in thepresent invention is to load MMC-treated human or murine blood cellswith self-antigens and to use these “inhibitory bullets” for targetedsuppression of specific self-reactive T cells in vitro and in vivo.

Thus, the problem is solved by the present invention, which provides apharmaceutical composition for treating an inflammatory disease in apatient, said composition comprising isolated immunosuppressive bloodcells treated with a therapeutically effective amount of achemotherapeutic agent, an autoantigen, and optionally apharmaceutically acceptable carrier.

For the purposes of convenience, “immunosuppressive blood cells” or“blood cells” are hereinafter referred to as “BC's”.

As used herein, the term “blood cells” (BC) refers to either whole bloodor distinct cell types within the whole blood having the desiredproperties. These distinct cell types include Peripheral BloodMononuclear Cells (PBMC) such as a lymphocytes or monocytes, ordendritic cells (DC).

Preferably, the “blood cells” are whole blood or PBMCs. PBMCs can beextracted from whole blood using ficoll, a hydrophilic polysaccharidethat separates layers of blood, with monocytes and lymphocytes forming abuffy coat under a layer of plasma. This buffy coat contains the PBMCs.Additionally, PBMC can be extracted from whole blood using a hypotoniclysis which will preferentially lyse red blood cells. This methodresults in neutrophils and other polymorphonuclear (PMN) cells which areimportant in innate immune defense to be obtained.

As used herein, the term “chemotherapeutic agent” encompasses any ofnumerous chemotherapeutic drugs that can be used in the compositions,methods or uses of the invention. These compounds fall into severaldifferent categories, including, for example, alkylating agents,antineoplastic antibiotics, antimetabolites, and natural sourcederivatives.

Examples of alkylating agents that can be used in the invention includebusulfan, caroplatin, carmustine, chlorambucil, cisplatin,cyclophosphamide (i.e., cytoxan), dacarbazine, ifosfamide, lomustine,mecholarethamine, melphalan, procarbazine, streptozocin, and thiotepa.

Examples of antineoplastic antibiotics include bleomycin, dactinomycin,daunorubicin, doxorubicin, idarubicin, mitomycin (e.g., mitomycin C),mitoxantrone, pentostatin, and plicamycin.

Examples of antimetabolites include fluorodeoxyuridine, cladribine,cytarabine, floxuridine, fludarabine, flurouracil (e.g., 5-fluorouracil(5FU)), gemcitabine, hydroxyurea, mercaptopurine, methotrexate, andthioguanine.

Examples of natural source derivatives include mycophenolate (mofetil),docetaxel, etoposide, irinotecan, taxanes (e.g. paclitaxel), teniposide,topotecan, vinblastine, vincristine, vinorelbine, prednisone, andtamoxifen.

Additional examples of chemotherapeutic agents that can be used in theinvention include asparaginase and mitotane. Furthermore, also C2ceramide can be used.

In an especially preferred embodiment, the chemotherapeutic agent isselected from the group consisting of mitomycin C, C2 ceramide,tunicamycin, mycophenolate-mofetil, tryptophan metabolites (andsemisynthetic derivates thereof), and proteasome inhibitors. Tryptophanmetabolites are also known as kynurenines, an example of which isTranilast.

Most preferably, the chemotherapeutic agent is mitomycin C.

The person skilled in the art is aware of a variety of antigens orderivatives thereof that can be used in the context of the presentinvention. These include natural antigens such as MBP (Myelin BasicProtein, human), MOG (Myelin Oligodendrocyte Glycoprotein), PLP(Proteolipid Protein), synthetic peptides such as Copaxone® (also knownas copolymer 1 or glatiramer acetate comprising a mixture of randomlysynthesized peptides using the following four amino acids: tyrosine,glutamic acid, alanine and lysine; the peptide sequences are based onthe naturally occurring human protein MBP) (Teva PharmaceuticalIndustries Ltd.), YEAK, VEAK, FEAK (other copolymers based on MBP₈₅₋₉₉)(Fridkis-Hareli et al., 2002, J. Clin. Invest., 109:1635-1643), naturalpeptides derived from the above antigens described in Bielekova et al.,2000, Nature Med., 6:1167-1175.), DNA coding for diverse myelinautoantigens, e.g. DNA encoding full length MBP, PLP, MOG, MAG (Ho etal., 2005, J. Immunol., 175.6226-6234), DNA coding for myelin-peptidesderived from the proteins MBP, MOG, PLP (Weissert et al., 2000, PNAS,97:1689-1694), antigens from clinical studies such as APL CGP77116(altered peptide ligand to MBP₈₃₋₉₉ (Bielekova et al., 2000, NatureMed., 6:1167-1175), APL NBI-5788 (altered peptide ligand to MBP₈₃₋₉₉(Kappos et al., 2000, Nature Med., 6:1176-1182), MBP₈₂₋₉₈ (BioMSTechnology Corp., AB, Canada) (Warren et al., 2006, Eur. J. Neurol.,13.887-895. Warren and Catz, 2000, Mutiple Sclerosis, 6:300-311) andBHT-3009 representing a DNA-construct encoding MBP (BayhillTherapeutics, Palo Alto, Calif., USA) (Bar-Or et al., 2007, ArchNeurol., 64:1407-1415; Bar-Or et al., 2005, Mutiple Sclerosis, 11:S167.Vollmer et al., 2005, Multiple Sclerosis, 11:S13).

In a preferred embodiment, the antigen used in the context of thepresent invention is myelin basic protein (MBP). Even more preferred asantigen is a synthetic peptide of MBP, such as Copaxone.

The composition of the present invention is used in the treatment of aninflammatory disease, which is another embodiment of the presentinvention.

As used herein, the term “treating” or “treatment” as used in relationto the treatment of inflammatory diseases is to be understood asembracing both symptomatic and prophylactic modes, that is the immediatetreatment, e.g. of acute inflammation (symptomatic treatment) as well asadvance treatment to prevent, ameliorate or restrict long termsymptomatology (prophylactic treatment). The term “treatment” as used inthe present specification and claims in relation to such diseases is tobe interpreted accordingly as including both symptomatic andprophylactic treatment, i.e. symptomatic treatment to ameliorate acuteinflammatory events and prophylactic treatment to inhibit ongoinginflammatory status and to ameliorate future bronchial exacerbationassociated therewith.

Preferably, “prophylactic treatment” refers to preventing the diseasesand disorders referred to in the present application. “Preventing”refers to retaining health with respect to the diseases or disordersreferred to herein for a certain period of time in a subject. It will beunderstood that the said period of time is dependent on the amount ofthe drug compound which has been administered and individual factors ofthe subject discussed elsewhere in this specification. It is to beunderstood that prevention may not be effective in all subjects treatedwith the compound according to the present invention. However, the termrequires that a statistically significant portion of subjects of acohort or population are effectively prevented from suffering from adisease or disorder referred to herein or its accompanying symptoms.Preferably, a cohort or population of subjects is envisaged in thiscontext which normally, i.e. without preventive measures according tothe present invention, would develop a disease or disorder as referredto herein. Alternatively, the prevalence of a disease in a cohort willbe significantly reduced with respect to the normal prevalence in acohort of subjects which have been efficiently prevented (protected)from the disease. Whether a portion is statistically significant can bedetermined without further ado by the person skilled in the art usingvarious well known statistic evaluation tools discussed below in thisspecification.

The term “symptomatic treatment” refers to ameliorating theaforementioned diseases or disorders or the symptoms accompaniedtherewith to a significant extent. In the case of organ graft rejectiontreatment, preferably, suppresses the rejection so far that thetransplanted organ(s) remain(s) functional. Also preferably,graft-versus-host disease is limited by the treatment to such an extentthat the patient's organs are not significantly damaged.

It is to be understood that treating as used in accordance with thepresent invention may not be effective in all subjects to be treated.However, the term shall require that a statistically significant portionof subjects suffering from a disease or disorder referred to herein canbe successfully treated. Whether a portion is statistically significantcan be determined without further ado by the person skilled in the artusing various well known statistic evaluation tools, e.g. determinationof confidence intervals, p-value determination, Student's t-test,Mann-Whitney test etc. Preferred confidence intervals are at least 90%,at least 95%, at least 97%, at least 98% or at least 99%. The p-valuesare, preferably, 0.1, 0.05, 0.01, 0.005, or 0.0001. Preferably, thetreatment shall be effective for at least 60%, at least 70%, at least80%, or at least 90% of the subjects of a given cohort or population.

As used herein, the term “inflammatory disease” refers to diseases whichare a result of an individual's immune reaction of connecting tissue andblood vessels to a stimulus, with the purpose to eliminate or inactivatesaid stimulus. Triggering effectors include mechanical stimuli, or otherphysical factors, e.g. ionizing radiation, UV light, heat, coldness;chemical substances, e.g. bases, acids, heavy metals, bacterial toxins,allergens, and immune complexes, as well as pathogens, e.g.microorganisms and viruses, worms and insects; and pathogenic metabolismproducts, malfunctioning enzymes, malign tumors.

As used herein, “therapeutically effective amount” means a sufficientamount of said compound to treat a particular disease, at a reasonablebenefit/risk ratio. In general, the term “therapeutically effectiveamount” shall refer to an amount of said compound which isphysiologically significant and improves an individual's health. Anagent, i.e. said compound, is physiologically significant if itspresence results in a change in the physiology of the recipient human.For example, in the treatment of a pathological condition,administration of said compound which relieves or arrests furtherprogress of the condition would be considered both physiologicallysignificant and therapeutically effective.

As indicated supra, the BC's of the present invention are useful in thetreatment of inflammatory diseases. Such inflammatory diseases can besubdivided into chronic inflammatory diseases, acute inflammatorydiseases, allergic inflammatory disorders, graft-versus-host rejectiondiseases, and autoimmune disorders, all of which are encompassed withinthe present invention. Among these subgroups, inflammatory diseases ofthe respiratory tract, inflammatory skin diseases, allergic inflammatorydisorders, inflammatory diseases of the gastrointestinal tract andinflammatory heart diseases can occur.

Preferably, the BC's of the present invention are useful in thetreatment of autoimmune disorders as listed hereinafter.

BC's may also be used to treat any disease or condition of the airwaysor lung requiring immunosuppressive therapy, e.g., for the treatment ofautoimmune diseases of, or as they affect, the lungs (for example, forthe treatment of sarcoidosis, alveolitis or chronic hypersensitivitypneumonitis) or for the maintainance of allogenic lung transplant, e.g.,following lung or heart lung transplantation.

In a further preferred embodiment of the present invention relates to apharmaceutical composition for the treatment of organ graft rejectionand/or graft-versus-host disease comprising isolated immunosuppressiveblood cells treated with a therapeutically effective amount of achemotherapeutic agent and optionally a pharmaceutically acceptablecarrier.

As immunosuppressants, BC's are useful when administered for theprevention of immune-mediated tissue or organ graft rejection. Examplesof transplanted tissues and organs which suffer from these effects areheart, kidney, liver, medulla ossium, skin, cornea, lung, pancreas,intestinum tenue, limb, muscle, nervus, duodenum, small-bowel,pancreatic-islet-cell, and the like; as well as graft-versus-hostdiseases brought about by medulla ossium transplantation.

A preferred embodiment of the present invention relates to thepharmaceutical composition of the present invention for the symptomatictreatment of organ graft rejection and graft-versus-host disease.Preferably, treatment of the rejection of the following organs andtissues is encompassed by the present invention: heart, kidney, liver,medulla ossium, skin, cornea, lung, pancreas, intestinum tenue, limb,muscle, nervus, duodenum, small-bowel and pancreatic-islet-cell.Graft-versus-host disease is, typically, brought about by medulla ossiumtransplantation. Preferably, the pharmaceutical composition comprisesBCs of the donor or the recipient. More preferably, in the case ofgraft-versus-host disease the BCs are taken from the recipient of thetransplant while in the case of organ graft rejection the cells aretaken from the donor.

Interestingly, it has been found in the study underlying the presentinvention that the pharmaceutical composition disclosed in thisapplication cannot only be used for the prophylactic treatment of anorgan graft rejection but also for its symptomatic treatment. Themechanisms that are required for the prophylactic treatment of organgraft rejection and for the symptomatic treatment thereof differconsiderably. Prophylactic treatment only requires the suppression ofrelatively few and inactive immune cells. In the naïve unstimulatedstate a frequency of about one precursor clone in 100,000 CD8+ T cellshad been estimated to exhibit specificity for a defined antigen(Blattmann et al., 2002, J. Exp. Med., 195:657-664).

In an acute organ graft rejection the immune cell clones which recognizetissue of the donor have already expanded. Regarding viral infections,within 7-8 days a massive increase in number of specific T-cell clonesoccurs, up to 50,000-fold comprising about 15 to 20 proliferation cycles(Williams & Bevan, 2007, Ann. Rev. Immunol., 25:171-192). Thus, theactivity of a large number of cells has to be suppressed successfully.Moreover active immune cells are in a different physiological state ascompared to resting immune cells. In order to initiate proliferation andvarious effector functions naïve CD4+ and CD8+ T cells need to encounterantigens in lymphoid organs presented by antigen-presenting cells(APCs). In contrast activated and expanded T cells swarm to theperipheral tissues to find and subsequently eliminate the antigenicsources. During this extremely complex procedure the activated cellsexpress a mixture of various signaling and effector molecules such ascytokines and chemokines that exhibit uncounted functions upon immune aswell as non-immune cells. The exposure to foreign antigens usuallyresults in the appearance of long-lived so-called memory cells making up5%-10% of the original number of activated effector cells. The qualityof the memory cells is reflected by a faster and more effective responseto further encounters with the same antigens (Harty & Badovinac, 2008,Nat. Rev. lmmunol., 8:107-119; Williams & Bevan, 2007, Ann. Rev.Immunol., 25:171-192; Sprent & Surh, 2002, Ann. Rev. Immunol.,20:551-579; Rogers et al., 2000, J. Immunol., 164:2338-2346. Therefore,the efficiacy of the pharmaceutical composition of the present inventionfor the symptomatic treatment of an organ graft rejection wassurprising.

Preferably, the blood cells in the pharmaceutical composition for thesymptomatic treatment of organ graft rejection and graft-versus-hostdisease are peripheral blood mononuclear cells.

The regulation of the immune response by BC's would particularly findutility in the treatment of autoimmune disorders, such as rheumatoidarthritis, systemic lupus erythematosis, hyperimmunoglobulin E,Hashimoto's thyroiditis, multiple sclerosis, progressive systemicsclerosis, myasthenia gravis, type I diabetes, uveitis, allergicencephalomyelitis, glomerulonephritis, and the like; and furtherinfectious diseases caused by pathogenic microorganisms, such as HIV. Inthe particular cases of HIV-1, HIV-2 and related retroviral strains,inhibition of T-cell mitosis would suppress the replication of thevirus, since the virus relies upon the host T-cell's proliferativefunctions to replicate.

In a preferred embodiment, the autoimmune disorder to be treated withthe pharmaceutical composition and method of the present invention ismultiple sclerosis.

Other treatable conditions would include but are not limited to ischemicbowel diseases, inflammatory bowel diseases, necrotizing enterocolitis,intestinal lesions associated with thermal burns and leukotrieneB4-mediated diseases; intestinal inflammations/allergies such as Coeliacdiseases, proctitis, eosinophilic gastroenteritis, and mastocytosis;food-related allergic diseases which have symptomatic manifestationremote from the gastrointestinal tract (e.g., migraine, rhinitis andeczema); renal diseases such as interstitial nephritis, Goodpasture'ssyndrome, hemolytic-uremic syndrome and diabetic nephropathy; nervousdiseases such as multiple myositis, Guillain-Barre syndrome, Meniere'sdisease, polyneuritis, multiple neuritis, mononeuritis andradiculopathy; endocrine diseases such as hyperthyroidism and Basedow'sdisease; hematic diseases such as pure red cell aplasia, aplasticanemia, hypoplastic anemia, idiopathic thrombocytopenic purpura,autoimmune hemolytic anemia, agranulocytosis, pernicious anemia,megaloblastic anemia and anerythroplasia; bone diseases such asosteoporosis; respiratory diseases such as sarcoidosis, fibroid lung andidiopathic interstitial pneumonia; skin disease such as dermatomyositis,leukoderma vulgaris, ichthyosis vulgaris, photoallergic sensitivity andcutaneous T cell lymphoma; circulatory diseases such asarteriosclerosis, atherosclerosis, aortitis syndrome, polyarteritisnodosa and myocardosis; collagen diseases such as scleroderma, Wegener'sgranuloma and Sjogren's syndrome; adiposis; eosinophilic fasciitis;periodontal disease such as lesions of gingiva, periodontium, alveolarbone and substantia ossea dentis; nephrotic syndrome such asglomerulonephritis; male pattern aleopecia or alopecia senilis bypreventing epilation or providing hair germination and/or promoting hairgeneration and hair growth; muscular dystrophy; Pyoderma and Sezary'ssyndrome; Addison's disease; active oxygen-mediated diseases, as forexample organ injury such as ischemia-reperfusion injury of organs (suchas heart, liver, kidney and digestive tract) which occurs uponpreservation, transplantation or ischemic disease (for example,thrombosis and cardiac infraction): intestinal diseases such asendotoxin-shock, pseudomembranous colitis and colitis caused by drug orradiation; renal diseases such as ischemic acute renal insufficiency andchronic renal insufficiency; pulmonary diseases such as toxinosis causedby lung-oxygen or drug (for example, paracort and bleomycins), lungcancer and pulmonary emphysema; ocular diseases such as cataracta,siderosis, retinitis, pigmentosa, senile macular degeneration, vitrealscarring and corneal alkali burn; dermatitis such as erythemamultiforme, linear IgA ballous dermatitis and cement dermatitis; andothers such as gingivitis, periodontitis, sepsis, pancreatitis, diseasescaused by environmental pollution (for example, air pollution), aging,carcinogenis, metastasis of carcinoma and hypobaropathy; disease causedby histamine or leukotriene-C4 release; Behcet's disease such asintestinal-, vasculo- or neuro-Behcet's disease, and also Behcet's whichaffects the oral cavity, skin, eye, vulva, articulation, epididymis,lung, kidney and so on.

In this context, the present invention further refers to the use of acomposition of the present invention for the manufacture of a medicamentfor the treatment of an autoimmune disease. The medicament, i.e. theblood cells treated as described above, maybe modified with methods andcompounds known to the skilled artisan in order to make them easilyadministrable to the patient. For example, pharmaceutically acceptablecarriers may be added as well.

For example, aqueous liquid compositions of the present invention may beparticularly useful for the treatment and prevention of various diseasesof the eye such as autoimmune diseases (including, for example, conicalcornea, keratitis, dysophia epithelialis corneae, leukoma, Mooren'sulcer, sclevitis and Graves' ophthalmopathy) and rejection of cornealtransplantation. In particular, compositions pertaining to the presentinvention are useful for treating a subject for immune-mediated organ ortissue allograft rejection, a graft-versus-host disease, an autoimmunedisease, an obstructive airway disease, a hyperproliferative disease, oran ischemic or inflammatory intestinal or bowel disease.

The specific therapeutically-effective dose level for any particularpatient will depend upon a variety of factors including the disorderbeing treated and the severity of the disorder; the age, body weight,general health, sex and diet of the patient; the time of administration,route of administration, the duration of the treatment; drugs used incombination or coincidental with BC's.

As used herein, the term “pharmaceutically acceptable carrier” means anon-toxic, inert solid, semi-solid or liquid filler, diluent,encapsulating material or formulation auxiliary of any type. Someexamples of materials which can serve as pharmaceutically acceptablecarriers are sugars such as lactose, glucose and sucrose; starches suchas corn starch and potato starch; cellulose and its derivatives such assodium carboxymethyl cellulose, ethyl cellulose and cellulose acetate;powdered tragacanth; malt; gelatin; talc; excipients such as cocoabutter and suppository waxes; oils such as peanut oil, cottonseed oil,safflower oil, sesame oil, olive oil, corn oil and soybean oil; glycols,such a propylene glycol; esters such as ethyl oleate and ethyl laurate;agar; buffering agents such as magnesium hydroxide and aluminumhydroxide; alginic acid; pyrogen-free water; isotonic saline; Ringer'ssolution; ethyl alcohol, phosphate buffer solutions; non-toxic,compatible lubricants such as sodium lauryl sulfate and magnesiumstearate; as well as coloring agents, releasing agents, coating agents,sweetening, flavoring and perfuming agents. Preservatives andantioxidants can also be present in the composition, according to thejudgment of the formulator.

The compositions may be administered to humans and other animals orally,rectally, parenterally, intracisternally, intravaginally,intraperitoneally, bucally, or as an oral or nasal spray. The term“parenteral” as used herein refers to modes of administration whichinclude intravenous, intramuscular, intraperitoneal, intrasternal,subcutaneous and intraarticular injection and infusion. Preferably, theadministration occurs intravenously, intramuscularly or subcutaneously.

Pharmaceutical compositions of this invention for parenteral injectioncomprise pharmaceutically-acceptable sterile aqueous or nonaqueoussolutions, dispersions, suspensions or emulsions, as well as sterilepowders for reconstitution into sterile injectable solutions ordispersions just prior to use. Examples of suitable aqueous andnonaqueous carriers, diluents, solvents or vehicles include water,ethanol, polyols (such as glycerol, propylene glycol, polyethyleneglycol, and the like), carboxymethylcellulose and suitable mixturesthereof, vegetable oils (such as olive oil), and injectable organicesters such as ethyl oleate. Proper fluidity may be maintained, forexample, by the use of coating materials such as lecithin, by themaintenance of the required particle size in the case of dispersions,and by the use of surfactants.

In another aspect, the present invention also provides a method ofproducing immunosuppressive blood cells, comprising exposing an isolatedblood cell sample to a chemotherapeutic agent and/or an autoantigen or aderivative thereof.

Preferably, the BC's are treated first with the autoantigen, and,subsequently with the chemotherapeutic agent, in a manner as describedin the example section. However, the person skilled in the art will beable to easily adjust the incubation times and amounts of antigen orchemotherapeutic agent in order to obtain the desired immunosuppressiveblood cells.

In some cases, it is desirable to add only the chemotherapeutic agentalone. This is the case, when e.g. donor whole blood or PBMC's are usedas immunosuppressive cells for inhibiting transplant rejections.Particularly preferred for this application are tryptophan metabolites(kynurenines). Also preferred for this application is mitomycin C.

The invention also provides a method for treating a patient sufferingfrom an autoimmune disease, said method comprising: a) obtaining a bloodcell sample; b) treating said blood cell sample with a chemotherapeuticagent and an autoantigen; and c) administering such treated blood cellsto said patient; wherein said treated blood cells ameliorate saidautoimmune disease in said patient.

In accordance with this aspect of the invention, blood cells are firstloaded or pulsed with one or more antigens, such as one or moreautoantigens, and then modified ex vivo with an chemotherapeutic agentas described below in the Example section. In one embodiment, the bloodcells are pulsed with one or more diabetogenic autoantigens such as GAD,an islet cell autoantigen (ICA), or autoantigen NRP-A7. In oneparticular embodiment, blood cells are pulsed with each of GAD 65, ICA512 and NRP-A7. Alternatively, blood cells may be pulsed with pancreaticislet lysates. In another embodiment, blood cells are pulsed withcollagen (for example, to treat arthritis). In another embodiment, bloodcells are pulsed with myelin basic protein (MBP) (for example, to treatmultiple sclerosis), or a derivative thereof, as described supra.

In a preferred embodiment, the blood cells are pulsed with MBP or aderivative, synthetic peptide thereof, and the autoimmune disease ismultiple sclerosis.

In yet another preferred embodiment of the present invention the bloodsample is first treated with the autoantigen and subsequently with thechemotherapeutic agent.

In another aspect, the present invention refers to a method for treatinga graft recipient, said method comprising a) obtaining a blood cellsample from a donor, b) treating said blood cell sample with achemotherapeutic agent, and c) administering such treated blood cells tosaid graft recipient, wherein said treated donor blood cells amelioratethe risk of developing graft rejection in said patient.

Furthermore, the present invention relates to a method for treating agraft recipient, said method comprising

a) obtaining a blood cell sample from a donor, wherein the recipient issuffering from organ graft rejection;

b) treating said blood cell sample with a chemotherapeutic agent; and

c) administering such treated blood cells to said graft recipient,wherein said treated donor blood cells ameliorate the ongoing organgraft rejection in said patient.

In a preferred embodiment, the chemotherapeutic agent is a tryptophanmetabolite, most preferably a kynurenine derivative, such as Tranilast.Also preferably, the chemotherapeutic agent is mitomycin C.

In another aspect, the present invention refers to a method for treatinga graft recipient, said method comprising

a) obtaining a blood cell sample from a recipient

b) treating said blood cell sample with a chemotherapeutic agent, and

c) administering such treated blood cells to said graft recipient,wherein said treated recipient blood cells ameliorate the risk ofdeveloping graft-versus-host disease initiated in said patient.

Furthermore, the present invention relates to a method for treating agraft recipient, said method comprising

a) obtaining a blood cell sample from a recipient, wherein the recipientis suffering from graft-versus-host disease;

b) treating said blood cell sample with a chemotherapeutic agent; and

c) administering such treated blood cells to said graft recipient,wherein said treated recipient blood cells ameliorate the ongoinggraft-versus-host disease in said patient.

In a preferred embodiment, the chemotherapeutic agent is a tryptophanmetabolite, most preferably a kynurenine derivative, such as Tranilast.Also preferably, the chemotherapeutic agent is mitomycin C.

DESCRIPTION OF THE DRAWINGS

FIG. 1. Effect of MMC-treated BCs loaded with MBP on resting oractivated T cells from MS patients. Primary stimulation (A, B):MBP-MMC-BCs are co-incubated with resting (A) (n=8) or activatedperipheral lymphocytes (B) (n=7). Negative controls: MBP-BCs orlymphocytes only; positive controls: MMC-untreated MBP-BCs pluslymphocytes. Restimulation (C, D): CD4+ cells are isolated andre-stimulated with MBP-BCs of the same donor. Abscissa shows CD4 cellspretreatment. Ordinate shows T-cell proliferation. The first columnrepresents BCs only (negative control). Data represent mean±SD and areexpressed as percentage of positive control values (MBP-loadedBCs+lymphocytes=100%).

FIG. 2. Influence of MMC-BCs culture medium on stimulated T cells.MMC-treated or untreated BCs are cultivated for 72 h. Supernatants(conditioned medium) are collected and used for cultures of anti-CD3antibody-stimulated T cells with or without autologous BCs. Controlsconsisted of BCs and lymphocytes only. Data represent mean±SD and areexpressed as percentage of positive control values(BC+anti-CD3+Iymphocytes=100%) (n=4).

FIG. 3. Cell cycle analysis of T cells exposed to MMC-BCs. Anti-CD3antibody-stimulated T cells are co-cultured with (A) untreated and (B)MMC-treated (25 μg MMC/ml) autologous BCs. Twenty four hrs aftersupplementation with 10 μM BrdU the cells are analyzed by flow cytometryusing a BrdU-Flow-Kit. The displayed quadrants show the percentage ofcells in the corresponding cell cycle (G0/G1, G2/M, S) as well as thatof dead cells.

FIG. 4. Flowcytometric analysis of apoptosis following treatment of BCswith MMC. BCs are treated with 50 μg/ml MMC and labelled withannexin-V-FITC and 7-AAD after 2, 6 and 24 hrs of incubation. Controlsconsisted of untreated BCs (−MMC). The lower and upper right quadrantshow apoptosis. Percentages of apoptotic cells are displayed.

FIG. 5. Effect of MMC-treated, MBP-presenting BC's in vivo. (A) Tg4 miceare injected i.v. with either MBP-BCs (♦) or MMC-treated MBP-BCs (▪).(B) Mice immunized in experiment A with MMC-treated MBP-BCs (▪) arechallenged on day 28 with MBP-loaded BCs. Mice immunized in experiment Awith MBP-BCs (♦) served as controls. Evaluation of EAE was performedaccording to the Coligan score. Data are shown as mean values±SEM (n=8per group).

FIG. 6. Prophylactic vaccination against EAE with MBP-loaded MMC-treatedBC's. (A) Tg4 mice are repetitively immunized with MBP-MMC-BCs. On day 0these (▪), as well as non-vaccinated mice (♦), are challenged withMBP-pulsed BCs. (B) The EAE severity (Coligan score) is shown, startingfrom day 10 after MBP-BC challenge. Data are displayed as mean±SEM (n=8non-vaccinated, n=10 vaccinated group).

FIG. 7. Phenotype of MMC-treated BCs. MMC-treated (50 μg/ml) and-untreated human BCs are labelled with FITC- or PE-conjugated specificmonoclonal antibodies to MHC class II, CD80, CD86, and expression ofmolecules was analyzed by flow cytometry with a FACScalibur. The bindingof antibodies is displayed in the histograms: filled grey histogramrepresents the isotype control, the red line binding to MMC-treated BCs,and the blue line to MMC-untreated BCs.

FIG. 8. Quantitative Real Time PCR of MMC-treated dendritic cells. TotalRNA of MMC-treated and untreated BCs was extracted 18 hours aftertreatment, reverse transcribed and analyzed by quantitative real timePCR based on the SYBR green method. Data are normalized to RNApolymerase II. The ordinate shows the fold change of RNA expressionlevels (±SEM) of MMC-treated BCs as compared to the untreatedcounterparts (for each gene n≧5)

FIG. 9. Effect of MMC-treated blood cells on CD4⁺-T cells in vivo.MBP-specific TG4 T cells are labelled with CFSE-dye and transferred i.v.to syngeneic B10.PL mice. After 24 h PBS (negative control)(top),MBP-loaded blood cells (positive control)(middle), orMBP-loaded/MMC-treated blood cells (bottom) are injected i.v. After 4days total lymph node cells are isolated and analyzed for CFSE-stainingof F23.1⁺ (Vβ8.2) CD4⁺ T cells. Data represent mean percentages ofCFSE^(low) proliferating T cells (MBP-MMC-BCs vs. PBS-group: p=0.031;MBP-MMC-BCs vs. MBP-BCs group: p=not significant).

The invention is further explained by the following examples withoutbeing bound to it by any theory.

EXAMPLES Examples 1 Experimental Procedures

(a) Mice

B10.PL mice were obtained from Jackson Laboratories (Bar Harbor, Me.).TCR-transgenic Tg4 mice (I-A^(u) background) express a TCR derived froman encephalitogenic CD4+ T cell clone specific for a MBP peptide (aa1-9)(9).

(b) Generation of Dendritic Cells

Murine DCs are generated from bone marrow cells of B10.PL mice accordingto the protocol of Lutz et al. (10). For activation, 0.5 μM CpG-ODN 1668is added. 90 min later non-adherent BMDC's are obtained. MMC (50 μg/m1)is added for 30 min of culture and the cells (10⁶/ml) are extensivelywashed. N-terminal acetylated MBP₁₋₁₀ peptide Ac-ASQKRPSQRS (Ac1-10) isadded at a concentration of 5 μM in combination with CpG-ODN. Human DCsare generated according to a standard protocol as previously described(11). For MBP-specific T cell studies, 30 μg/ml MBP (Sigma-Aldrich) isadded to immature DCs until maturation. MMC (10-100 μg/ml) is added tothe DC culture medium; after 30 min of incubation the cells are washed.

(c) T-cell Studies In Vitro

Murine lymphocytes are cultured with BM-derived BCs. Human peripheralblood lymphocytes of MS patients are co-incubated with autologousMBP-loaded BCs. In a parallel experiment, DRB1*0301-BCs from healthydonors are loaded with MBP and co-incubated with MBP-specific CD4⁺ Tcells (clone ES-BP8T) as previously described (11).

In a control experiment, the BCs are loaded with an irrelevant peptidewith comparable interaction with DRB1*0301. The HLA restriction can becalculated by the SYFPEITHI software (www.uni-tuebingen.de/uni/kxi).Co-cultures are performed at a BC:T cell ratio of 1:10. T cellproliferation is measured by [³H]thymidine incorporation.

(d) Supernatants of MMC-BCs

Mature BCs are treated with 25, 50 or 75 μg/ml MMC and washed. After 72h of additional incubation the supernatants are collected and used ascell culture medium in a T-cell proliferation assay. 2×10⁵ cells/wellare stimulated for 4 days with anti-CD3 monoclonal antibody (dilution1:6400).

(e) Cell Cycle Analysis

Lymphocytes are stimulated for 2 days with anti-CD3 monoclonal antibodyand cell cycle analysis is performed using the BrdU Flow Kit (BDPharmingen, Heidelberg, Germany). Cells (10⁶) are incubated overnightwith 10 μM BrdU. After fixation, permeabilization and treatment with 300μg/ml DNase, the cells are stained with FITC-labeled anti-BrdU antibodyand 7-AAD and analyzed by flow cytometry

(f) EAE Model

EAE is induced by i.v. injection of 5×10⁶ activated BCs (in 0.2 ml)pulsed with 5 μM of autoantigenic MBP peptide (+/−MMC). On day 1 and 2after immunization, each mouse is injected i.p. with 200 ng pertussistoxin (Calbiochem, Darmstadt, Germany) in 500 μl DPBS. Symptoms areevaluated daily according to the Coligan score.

(g) Affymetrix Microarray

RNA is converted into ds-cDNA using T7-(dT)₂₄ primers and theSuperscript Choice system (Invitrogen, Karlsruhe, Germany).Biotin-labeled cRNA is generated from the cDNA sample, hybridized toU133 Plus 2.0 gene chips (Affymetrix, High Wycombe, UK), stained withstreptavidin-phycoerythrin (MoBiTec, Gottingen Germany) and scannedusing the GeneArray scanner (Affymetrix). Microarray data of samplesderived from 3 unrelated BC donors are analyzed using the AffymetrixData Mining tool (DMT 4.0), the Affymetrix publishing tool (MDB 3.0),and the statistical data analysis software (Affymetrix Microarray Suite5.0). Comparisons between MMC-treated and untreated BCs are done forgenes with a positive detection call in at least one experimental groupand with a fold change of at least 3 (corresponding to a signal logratio between the two experimental groups of less than −1.5 or more than1.5). Functional classifications from Gene Ontology (GO) Consortium(http://www.geneontology.org) are assigned to each identified gene.

(h) FACS Analysis

Human BCs are stained with fluorescein isothiocyanate (FITC)-labeledannexin V and 7-amino-actinomycin (7-AAD) to confirm apoptotic celldeath.

BC staining is performed with fluorescence (FITC, PE)-labeled monoclonalantibodies (to MHC II, CD80, CD86,) to concentrations indicated by themanufacturers (BD Biosciences).

(i) Approval for Animal and Human Studies

Animal experiments are approved by the Animal Welfare Board of theGovernmental Office Karlsruhe. Studies of human sera and cells areapproved by the University of Heidelberg Ethics Committee

(k) Statistics

Results are shown as mean±SD or SEM as indicated. Single values of Tcell proliferation represent the mean [³H]thymidine incorporation (cpm)of triplicate cultures and are given in percentage of the positivecontrol (=100% proliferation) or cpm. P values are calculated by theunpaired Student's t-test using SigmaStat software (SPSS). Statisticalsignificance is set at p<0.05.

Example 2 Results

Myelin-specific T cells have been proposed to play a role in thepathogenesis of MS (1, 4). Therefore, MBP represents a candidate antigenfor specific immunotherapy in MS. In the following experiments westudied the capacity of MMC-BCs loaded with MBP to control the activityof specific T cells derived from MS patients in cell cultures, and wetested their action in a mouse EAE model.

(a) Myelin-Basic-Protein-Loaded MMC-BCs Inhibit Specific T Cells ofMultiple Sclerosis Patients In Vitro

BCs derived from MS patients are loaded with MBP and co-incubated withautologous T cells. In a parallel experiment, the BCs are loaded withMBP and treated with MMC. Whereas untreated BCs induce strong T cellstimulation, MMC-BCs do not (FIG. 1A).

Therapy of patients with active MS should address already activatedautoreactive T cells. In order to find out whether these lymphocytes canbe controlled by inhibitory BCs, pre-activated MBP-specific T cellsderived from a MS patient are incubated with HLA-DR-matched, MBP-loadedMMC-BCs. The response of these T cells was significantly reduced (FIG.1B).

In the next experiment we investigated whether suppressed T cells can berestimulated with naïve MBP-loaded BCs of the same donor. The resultsshow that, once suppressed by MMC-BCs, T cells cannot or can only weaklybe re-activated (FIG. 1C, FIG. 1D).

(b) Supernatants of Mitomycin-Treated BC's Do Not Inhibit the T Cells

Upon treatment of BCs with MMC a certain amount of substance might havediffused from the intracellular compartment into the culture medium andblocked T cell proliferation. In order to exclude that, supernatants ofMMC-treated BCs are collected and used as medium in T cell proliferationassays. The results showed that T cell proliferation is not affected(FIG. 2), indicating that leakage of MMC from treated cells is not thereason for suppression.

(c) T Cells are Blocked in the G0/G1 Phase

When analyzing the mechanism of suppression, two aspects must beconsidered: the reaction of T cells to inhibitory BCs and the molecularchanges of BCs induced by MMC-treatment.

As shown in the previous experiment, re-stimulation of suppressed Tcells is not or only partially possible, indicating that the cellseither became areactive or died. Cell cycle analysis revealed asignificant accumulation in the G0/G1 phase of T cells co-incubated withMMC-BCs (FIG. 3). This finding argues for induction of T cellareactivity. (d) Mitomycin C Does Not Inhibit the Expression of MHC-IIand CD80/86 on BC's

MMC might have changed the expression of MHC II or CD80/86. FACSanalysis showed that MHC II and CD80/86 are not down-regulated uponincubation with MMC (mean channel of MMC-treated/untreated BCs: MHCII=757/745; CD80=759/728; CD86=751/744); therefore, reduced antigenpresentation by lower MHC II density, or less co-stimulation by lowerC80/CD86 expression, cannot serve as an explanation for the inhibited Tcell proliferation.

(e) Mitomycin C Modulates the Expression of Apoptotic andImmunoregulatory Genes of BC's

A comprehensive gene scan of 47,000 transcripts and additional variantswas carried out by affymetrix microarray analysis. Genes whoseexpression was changed more than 3-fold upon treatment of BCs with MMCin 3 independent experiments are further analyzed. Based on thiscriterion, 116 genes are identified. Among the affected genes, two mainclusters are found: one involved in apoptosis and the other mediatingimmunosuppression. Among apoptosis-related genes, 6 pro-apoptotic genesare upregulated (LRDD, TNFRSF 10b, PERP, FDXR, TRAF4, DDIT3) and 5anti-apoptotic genes downregulated (NRG2, CFLAR, I-FLICE, Usurpin,FLAME-1), pointing to induction of cell death by apoptosis. It has beenspeculated that apoptotic cells are tolerogenic (12, 13). Therefore, itwas important to verify by FACS whether the changed expression of thesegenes had repercussions on cell viability. As shown in FIG. 4,MMC-treated BCs enter earlier into apoptosis than untreated BCs.Interestingly, in parallel to apoptotic genes, well knownimmunosuppressive genes (ADM, TSC22D3, LILRB4)(14-16) are upregulatedalong with a series of potentially inhibitory genes (MAFB, CSF2RA,MAP4K4, GAB2)(17-21). Taken together, these findings indicate inductionof apoptosis and increased expression of immunosuppressive genes in BCstreated with MMC.

(f) Myelin-Basic-Protein-Loaded MMC-BCs Inhibit Specific Mouse T CellsIn Vitro

We addressed the question whether the suppressive effect mediated byMMC-BCs in vitro also works in vivo. For clarifying this point, a mouseEAE model is chosen—a setting in which MBP-specific T cells cause aninflammatory disease, similar to the inflammation of MS in humans. Aprerequisite for their effectiveness in vivo is that, similarly to humanBCs, MMC-treated mouse BCs are T-cell suppressive in vitro. Cell culturestudies showed that mouse BCs loaded with MBP and treated with MMCsignificantly suppress specific syngeneic T cells of Tg4 mice(MBP-MMC-BCs+T cells=12,653±923 vs. MBP-BCs+T cells=24,727±3197; naïveBCs+T cells=7007±1591) (mean of cpm±SEM) (p=0.022).

Previous observations of Liu et al. (13) showed that, when injected intomice, antigen-loaded tolerogenic cells first drive antigen-specific Tcells into cell-cycle, and subsequently the T cells are inactivated.This finding prompted us to trace the fate of the deleteriousautoreactive T cells in animals treated with inhibitory BCs.MBP-specific T cells are labelled ex vivo with CFSE and injected intosyngeneic mice. Thereafter, the animals are injected i.v. withMBP-loaded BCs treated with MMC, and T cells are isolated and analyzedby FACS. The MBP-specific T cells showed a significant degree ofproliferation (MBP-MMC-BC=25% vs. MBP-BC=22%). Evidently, in spite ofinitial stimulation, the T cells must have been subsequently inactivatedbecause, as shown in the following in vivo experiment, they are not ableto cause EAE. This finding is in line with the observation described byLiu et al. (13).

(g) Vaccination with Myelin-Basic-Protein-Loaded MMC-BCs Protects MiceFrom Experimental Autoimmune Encephalitis

MBP-loaded untreated BCs are injected into animals and, as expected,severe EAE occurs within 2-3 weeks (FIG. 5A). If MBP-loaded BCs arepretreated with MMC and then injected, however, the animals remaincompletely free of symptoms, showing that MBP-specific T cells are notactivated. An interesting question is whether the symptom-free animalsbecame resistant to EAE. To this end, treated animals are re-challengedwith MBP-BCs. One must keep in mind that the transgenic Tg4 mice used inour study carry >90% MBP-specific T cells, in contrast to only <0.0001%in normal rodents (9, 22). We suspect that it might be difficult toinactivate such a large number of T cells with one injection only. In asubsequent experiment, therefore, the animals are treated 5× withMBP-MMC-BCs and then re-challenged (FIG. 6A). As shown in FIG. 6B, thistime the result is positive: whereas controls, which had not beenvaccinated with MBP-MMC-BCs, developed severe EAE with lethal outcome,pre-vaccinated mice recovered after a mild episode of disease.

Example 3 Discussion

Attempts to generate regulatory blood cells, in particular dendriticcells (DCs) for control of autoimmune reactions have recently beendescribed. Enk's group generated suppressive DCs by incubating the cellsin vitro with IL-10 and inhibited ovalbumin-specific CD4 T-cellresponses in naïve and sensitized mice (23). Huang et al. (24) observedthat a subpopulation of immature bone marrow-derived DCs, if pulsed withMBP and injected into syngeneic rats, protected from clinical EAE.Others showed that, to the contrary, mature but not immature DCsinjected into mice with EAE reduced the severity of clinical signs andinflammation in the CNS (25). These conflicting findings stress thefunctional plasticity, from immunostimulation to suppression, of DCsunder various conditions. Clinical signs of disease could also bereduced if rats or mice with incipient EAE are injected withinterferon-y-treated DCs (26). In neither of the latter two studies areantigen-specific DCs used. By contrast, Menges et al. (27) usedtumor-necrosis-factor-a matured DCs pulsed with auto-antigenic peptideand observed protection from EAE if the mice are injected beforeinductive immunization. Another experimental study suggested thatinhibition of NF-kB by pharmacological agents enhanced the capacity ofimmature DCs to induce antigen-specific suppression to self antigens inmice (28). When murine DCs are transduced with the gene for suppressorof cytokine signaling (SOCS)-3, they exhibited a DC2 phenotype thatpromoted Th2 cell differentiation and weakly influenced autoimmunereactions in vivo (29). The severity of EAE in mice could also bereduced with autoantigen-loaded DCs expressing TRAIL or PDL1 transgenes(30).

Different functional behaviors of DCs belonging to the same maturationalstage (5, 6), the difficulty to standardize the generation ofsuppressive DCs by biological agents, and reversible modificationsinduced by cytokines or other biological agents, all are hurdles for theuse of suppressive DCs in clinical trials, entailing the risk ofstimulating instead of inhibiting the immune response. Ideally,inhibitory DCs for clinical application should be easily andreproducibly generated, stable in their suppressive action, and capableof irreversibly inactivating autoreactive T cells.

Based on our previous experience in rats (8), in which allograftrejection was successfully controlled by MMC-BCs, stably inhibitory DCsfor control of autoimmunity are generated in the present study bytreating the cells with MMC and loading with autoantigen. These cellsprotected animals from lethal EAE, showing that, in principle, effectiveprophylactic vaccination against T cell mediated autoaggression ispossible. MMC is an alkylating agent used in cancer therapy whichstrongly binds to distinct DNA sites, cross-links the double helicalstrands, inhibits DNA synthesis, and consequently suppresses cellproliferation. In addition, MMC inhibits RNA and protein synthesis.Interestingly, alkylating agents not only inhibit but also activatepathways usually triggered by stimulatory agents (31). Therefore, it isnot surprising that in our model the expression of certain DC-genes wasup-and not down-regulated. Because of the irreversible interaction ofMMC with intracellular compounds, cells do not release MMC uponincubation with this substance. This was confirmed by our finding thatsupernatants of MMC-treated DCs do not suppress T cell reactions. Mostimportantly, in contrast to manipulations of DCs with biological agents(e.g. cytokines), MMC-treatment induces irreversibly suppressive DCs byinduction of apoptosis, a feature that offers a potential for developinga stable therapeutic tool. Another advantage of this model is the use ofnon-toxic doses of a clinically approved drug. The therapeutic dose ofMMC is 10-20 mg/m²; the concentration of MMC used in this study forincubation of cells was 0.05-0.100 mg/ml. Our analyses showed that afterextensive washing the cell suspension contained, if at all, non-activetraces of MMC. No clinical side effects are expected at these minimalamounts of free MMC in the injected solution.

Our findings demonstrate that MMC-BCs are effective in controlling bothmouse and human autoreactive T cells. Previous studies in our laboratoryshowed that MMC-BCs are strongly inhibitory in rats (8). In differenceto other models, the therapeutic tool described herein works acrossspecies. Moreover, in the present study the in vivo effect was testedunder aggravating conditions. Normal rodents carry less than 10⁻⁶MBP-reactive T cells in their repertoire (22). We used TG4 transgenicmice with >90% MBP-reactive T cells and consequently with an extremeproneness to EAE (9). If this huge number of “dangerous” T cells can bekept in check, we can expect a reliable effect when lower numbers ofautoreactive T cells are involved.

Concerning the mechanism of suppression of autoreactive T cells derivedfrom MS patients, we were concerned that MMC-BCs simply might “lose”their stimulatory capacity due to cell death. Our findings, however,show that suppressed T cells cannot be reactivated. Moreover, animalsvaccinated with autoantigen-loaded inhibitory DCs became areactive tore-stimulation with the same antigen. These are signs of activesuppression instead of a lacking immune response.

A previous study showed that exposure to necrotic tumor cells, incontrast to exposure to apoptotic cells, induces immunostimulation (12).This, as well as other observations (13), led to the hypothesis thatnecrotic cell death is immunogenic, whereas apoptotic cell death ispoorly immunogenic or even tolerogenic. From a physiological standpointof view this makes sense, because apoptosis is the normal process ofcell death in our tissues. Would apoptosis induce immune responses, itwould lead to inflammation and autoimmunity. Liu et al. (13) used thisphenomenon to actively induce tolerance. Dying apoptotic splenocytes areloaded with ovalbumin and injected into syngeneic mice. After an initialphase of T cell stimulation the recipients became tolerant to ovalbumin(13). It is interesting to note the reports showing that DC lifespan hasimportant consequences for DC-T-cell interaction, and thus determinesthe immunological outcome. Hugues et al. concluded that stableinteractions favor T cell priming, whereas brief contacts between DCsand T cells may contribute to the induction of T cell tolerance (32). Inthe present series of experiments, MMC accelerated the natural processof apoptosis, shortening the lifespan of injected DCs and thus theircontact with T cells. This provides a possible explanation for theobserved tolerogenic effect. Obeid et al. (33) has recently analyzed theimmunogenic potential of tumor cells rendered apoptotic by variouschemotherapeutic drugs and observed that anthracyclins generatestimulatory cells whereas other drugs, such as mitomycin C, do not. Ifanthracyclins are used, the chaperon protein calreticulin wasupregulated and responsible for the stimulatory action. This finding isimportant for tumor therapy, which aims at killing malignant cells andconcomitantly stimulating the immune response against the tumor. Ourfindings are interesting in this context by demonstrating that treatmentwith MMC renders the cells apoptotic but—as shown by affymetrixmicroarray—does not upregulate calreticulin; instead, it upregulatesimmunosuppressive molecules. Whereas the observation of Obeid et al.(33) may be used for improving chemotherapy in cancer, our observationhas a therapeutic potential for controlling autoimmune disease or graftrejection.

In the present study, induction of apoptosis was suggested byupregulation of pro-apoptotic genes, including LRDD (coding for PIDD),TNFRSF10b (coding for TRAIL-R2), PERP, FDXR, TRAF4, and DDIT3.Additionally, we noted downregulation of genes which protect fromapoptosis, such as NRG2 and CFLAR (coding for cFLIP and its variantsI-FLICE, usurpin, FLAME-1). Most importantly, apoptosis of MMC-treatedDCs was demonstrated by FACS.

Gene expression analysis showed that, concomitantly with induction ofapoptosis, a series of strongly immunosuppressive genes are upregulated.ADM (adrenomedullin), whose expression was increased 10 times, is apeptide that prevents sepsis-induced mortality, abrogates colitis, andprovides highly effective therapy of arthritis by decreasing thepresence of autoreactive Th1 cells, inducing regulatory T cells andinhibiting autoimmune and inflammatory responses (14). Another genewhose expression was upregulated by MMC was TSC22D3 (coding for GILZ).Interestingly, the same gene is upregulated upon exposure of DCs toglucocorticoids, IL-10, or TGF-β, all well-known immunologicalinhibitors (15). GILZ confers a suppressive phenotype to DCs andprevents them from activating T cells (15). A molecule induced by GILZis LILRB4 (coding for ILT3), a protein which renders monocytes and DCstolerogenic and has clinical relevance (16). Human heart transplantrecipients with stable grafts have circulating T suppressor cells whichupregulate ILT3 in donor antigen-presenting cells (16). These findingsdemonstrate an important immunoregulatory function of ILT3. We found asignificant increase of ILT3 expression in MMC-BCs. Other functionallyrelevant genes whose expression was modulated by MMC are MAFB-whichdirects differentiation away from DCs towards monocytes (17),CSF2RA—which transduces GM-CSF signals (18), MAP4K4—which mediates TNF-asignalling and cell migration (19, 20), and GAB2—which transmits signalsdelivered by cytokine-, growth factor-, and antigen-receptors (21). Allof them might play a role in immunosuppression induced by MMC-treatedDCs.

Taken together, the observations of Obeid et al. (33) and ours suggestthat induction of apoptosis with concomitant upregulation of activatorymolecules renders cells immunogenic, whereas apoptosis and upregulationof inhibitory molecules renders cells immunosuppressive.

In the 1970s, a random copolymer of amino acids, termed glatirameracetate, was developed to mimic the composition of MBP. In clinicaltrials, glatiramer slowed progression of disability and significantlyreduced the relapse rate of MS (34). Studies showed that the copolymertolerized against a variety of different myelin antigens. More recently,altered peptide ligands of MBP and other auto-antigens constructed bysubstituting amino acids at the contact sites of these epitopes with theT cell receptor showed similar effects in animal models (4). These andother observations (35) indicate that the use of a single epitope caninhibit a disease caused by reactivity to multiple self-epitopes bydirecting unspecific regulatory mechanisms towards a certain organ.Apparently, in contrast to epitope “spreading”, epitope “containment” isalso possible. Based on these observations, it is conceivable thatMMC-BCs loaded with MBP, although addressing the immune response to oneantigen, also can control reactions to neighboring molecules. An elegantvariant of our model would be to load the inhibitory DCs with glatirameracetate or other altered peptides derived from autoantigens. Thesuppressive action of peptides would be expected to be amplified.

Our in vivo data are derived from studies in the murine EAE model. Ithas been questioned to which extent this model reflects the pathogenesisof MS in humans (1). Of course, no mouse data, including those derivedfrom EAE studies, can be automatically extrapolated to humans. It isworth mentioning, however, that in spite of all criticism 3 therapeuticcompounds approved for use in MS—glatiramer acetate, mitoxantrone andnatlizumab—emerged directly from findings in the EAE model (36). Ourobservations in mice gain additional relevance by the finding that Tcells of MS patients are also suppressed by MBP-loaded MMC-BCs.

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1-15. (canceled)
 16. A method of producing immunosuppressive blood cellscomprising: (a) exposing an isolated blood cell sample to achemotherapeutic agent; and (b) optionally exposing the isolated bloodcell sample to an autoantigen or a derivative thereof.
 17. The methodaccording to claim 16, wherein the exposure takes place in vitro. 18.The method according to claim 17, wherein the blood cell sample is firsttreated with the autoantigen and subsequently with the chemotherapeuticagent.
 19. A method for treating a patient suffering from an autoimmunedisease, the method comprising: (a) obtaining a blood cell sample; (b)treating the blood cell sample with a chemotherapeutic agent and anautoantigen; and (c) administering such treated blood cells to thepatient; wherein the treated blood cells ameliorate the autoimmunedisease in the patient.
 20. A method for treating an inflammatorydisease, organ graft rejection or graft-versus-host disease in a patientcomprising administering to the patient a composition comprising (a)isolated blood cells treated with a therapeutically effective amount ofa chemotherapeutic agent and optionally an autoantigen or a derivativethereof, and (b) optionally a pharmaceutically acceptable carrier. 21.The method of claim 20, wherein the chemotherapeutic agent is selectedfrom the group consisting of mitomycin C, C2 ceramide, tunicamycin,mycophenolate-mofetil, tryptophan metabolites, semisynthetic derivatesthereof, proteasome inhibitors, and a combination of two or more agents.22. The method of claim 21, wherein the chemotherapeutic agent ismitomycin C.
 23. The method of claim 20, wherein the autoantigen isselected from the group consisting of natural antigens, syntheticpeptides and natural peptides.
 24. The method of claim 23, wherein theautoantigen is a synthetic peptide of the myelin basic protein.
 25. Themethod of claim 24, wherein the synthetic peptide of the myelin basicprotein is copaxone.
 26. The method of claim 20, wherein the disease isorgan graft rejection or graft-versus-host disease and the blood cellsare only treated with a chemotherapeutic agent.
 27. The method of claim26, wherein the chemotherapeutic agent is mitomycin C.
 28. The method ofclaim 20, wherein the isolated blood cells are whole blood or peripheralblood mononuclear cells.